while camping one weekend, I realized I forgot my windscreens for a Sunday show I was hitting on my way home. In a pinch, I stopped at a dollar store, and picked up some generic nerf basketball sets (the kind you hang on the back of your door) and went next door to the joann fabrics, and picked up a yard of fake fur. Total investment was around 5 dollars.
You might be able to find a windscreen at radio shack to cut up and fit them for the church cards, or wonder around, and see what you can come up with. I would test at home before using any MacGyver solution to make sure you'll be happy with the results before the show.